In advance of design, permitting, and construction of a pipeline to deliver North Slope natural gas to out-of-state customers and Alaska communities, the Division of Geological & Geophysical Surveys (DGGS) has acquired lidar (light detection and ranging) data along proposed pipeline routes, nearby areas of infrastructure, and regions where significant geologic hazards have been identified. Lidar data will serve multiple purposes, but have primarily been collected to (1) evaluate active faulting, slope instability, thaw settlement, erosion, and other engineering constraints along proposed pipeline routes, and (2) provide a base layer for the state-federal GIS database that will be used to evaluate permit applications and construction plans. Lake polygons represent areas of water bodies (excluding streams and rivers) > 150 square meteres, present at the time of lidar data collection.

Supplemental_Information:

This metadata file was written to document and describe, as a whole, all the lake polygon files generated for this project. The original metadata files provided by Watershed Sciences, Inc. are also included in the download package and may provide additional useful information that is specific to each file. The metadata files provided by Watershed Sciences, Inc. have not been reviewed for accuracy or compliance with FGDC standards. The DGGS metadata standard extends the FGDC standard to include several elements that are required to facilitate internal data management.
For each data delivery area, reports documenting data collection methodology, accuracy, and quality control were provided by Watershed Sciences and the Oregon Department of Geology and Mineral Industries (DOGAMI). These reports have been combined into single comprehensive reports organized by delivery region. The lidar QC report (the comprehensive report from DOGAMI) and the lidar delivery report (the comprehensive report from Watershed Sciences) can be found at <http://dx.doi.org/10.14509/22722>. Information about the quadrangles included in individual delivery regions can be found in the lidar delivery index report included with the data download. The DGGS metadata standard extends the FGDC standard to include several elements that are required to facilitate internal data management. This dataset is described as a single layer titled:

Planar coordinates are encoded using coordinate pair
Abscissae (x-coordinates) are specified to the nearest 1.000000
Ordinates (y-coordinates) are specified to the nearest 1.000000
Planar coordinates are specified in meters

The horizontal datum used is North American Datum of 1983.
The ellipsoid used is Geodetic Reference System 80.
The semi-major axis of the ellipsoid used is 6378137.
The flattening of the ellipsoid used is 1/298.257222.

Data collection was supported by funding from the Department of Natural Resources (DNR), Division of Geological & Geophysical Surveys (DGGS), the Alaska Gas Pipeline Project Office, the Office of the Federal Coordinator, and the Alaska Gasline Development Corporation (AGDC). Lidar data were collected and processed by Watershed Sciences of Corvalis, Oregon. Survey data were collected by McClintock Land Associates of Eagle River, AK. Lidar data and derivative products were checked for quality, completeness, and accuracy by State of Oregon Department of Geology & Mineral Industries based in Portland, OR.

Acquisition: The lidar data were collected between September and October 2010 and between May and July 2011. The survey used the Leica ALS 60 system. Near-nadir scan angles were used to increase penetration of vegetation to ground surfaces. Ground-level GPS and aircraft IMU were collected during the flight.

Date: 2010 (process 2 of 3)

Processing lidar data: (1) Flight lines and data were reviewed to ensure complete coverage of the study area and positional accuracy of the laser points. (2) Laser point-return coordinates were computed using ALS Post Processor software, IPAS Pro GPS/INS software, and Waypoint GPS, based on independent data from the lidar system, IMU, and aircraft. (3) The raw lidar file was assembled into flight lines per return with each point having an associated x, y, and z coordinate. (4) Visual inspection of swath-to-swath laser point consistencies in the study area were used to perform manual refinements of system alignment. (5) Custom algorithms were designed to evaluate points between adjacent flight lines. Automated system alignment was computed based on randomly selected swath-to-swath accuracy measurements that consider elevation, slope, and intensities. Specifically, refinement in the combination of system pitch, roll, and yaw-offset parameters optimize internal consistency. (6) Noise (e.g., pits and birds) was filtered using ALS postprocessing software, based on known elevation ranges, and included the removal of any cycle slips.

Date: 2010 (process 3 of 3)

Hydro-flattening: A combination of automated and manual detection and adjustment techniques was used to identify lake boundaries and water levels for closed water bodies with a surface area > 150 square meters.

The accuracy of the lake polygons depends on the horizontal and vertical positional accuracy of the lidar data, the accuracy of the laser return classification and the accuracy of the hydro-flattening process. Refer to the lidar delivery report and lidar QC report for more details on the accuracy of the lidar data for each delivery area, including a comparison of GCP elevations with bare-earth DEM elevations. More information on the hydro-flattening process can also be found in the lidar delivery report.

Accuracies of lake boundaries is uncertain and variable depending on the accuracy of the lidar return classification and algorithms used for lake-edge detection, but is believed to be within a few meters.

The following logical consistency tests were performed. 1) All lake polygons were checked to ensure that lidar data within the polygons was classified as water. 2) All lake edge lines were manually reviewed and edited in a 3-D environment by the contractor.

This report, map, and/or dataset is available directly from the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys (see contact information below).

Use_Constraints:

Any hard copies or published datasets utilizing these datasets shall clearly indicate their source. If the user has modified the data in any way, the user is obligated to describe the types of modifications the user has made. The user specifically agrees not to misrepresent these datasets, nor to imply that changes made by the user were approved by the State of Alaska, Department of Natural Resources, Division of Geological &amp; Geophysical Surveys. The State of Alaska makes no express or implied warranties (including warranties for merchantability and fitness) with respect to the character, functions, or capabilities of the electronic data or products or their appropriateness for any user's purposes. In no event will the State of Alaska be liable for any incidental, indirect, special, consequential, or other damages suffered by the user or any other person or entity whether from the use of the electronic services or products or any failure thereof or otherwise. In no event will the State of Alaska's liability to the Requestor or anyone else exceed the fee paid for the electronic service or product.

The State of Alaska makes no expressed or implied warranties (including warranties for merchantability and fitness) with respect to the character, functions, or capabilities of the electronic data or products or their appropriateness for any user's purposes. In no event will the State of Alaska be liable for any incidental, indirect, special, consequential, or other damages suffered by the user or any other person or entity whether from the use of the electronic services or products or any failure thereof or otherwise. In no event will the State of Alaska's liability to the Requestor or anyone else exceed the fee paid for the electronic service or product.

Current publication is not available on paper. To purchase other printed reports and maps, contact DGGS by phone (907-451-5020), e-mail (dggspubs@alaska.gov), or fax (907-451-5050). Payment accepted: Cash, check, money order, VISA, or MasterCard.

DGGS publications are available as free online downloads or you may purchase paper hard-copies or digital files on CD/DVD or other digital storage media over the counter, by mail, phone, fax, or email from the DGGS Fairbanks office. Turnaround time is 1-2 weeks unless special arrangements are made and an express fee is paid. Shipping charge will be the actual cost of postage and will be added to the total amount due. Contact us for exact shipping amount.